Effect of Ph Level and Hydrogen Peroxide on Catalase (2023)

Paper Type: Free EssaySubject: Biology
Wordcount: 1572 wordsPublished: 23rd May 2018

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The investigation was carried out to determine how different ph levels and hydrogen concentrations, affect the activity of catalase in potato during the decomposition of hydrogen peroxide to produce water and oxygen. Different variables (independent, dependent and controlled) were put into consideration during the laboratory session to find out how much oxygen was produced. The test was carried out, using potato as a source of catalase and reacting it with hydrogen peroxide and ph. Five different ranges were used for the two variables and each test was repeated 3 times with new pieces of potato discs and the volume of oxygen was measured. The result of the investigation showed that, the enzyme catalase worked at its optimum at 30% which was the highest range available and an optimum ph of 9. The result above illustrates that catalase in potato works best at high ph levels and substrate concentrations.


The purpose of this experiment was to determine the optimal substrate concentrations and ph levels under which enzymatic reactions involving the enzyme catalase will occur successfully. Catalase is a heme containing enzyme usually found in high concentrations in cellular organelles called peroxisomes (www1).

Catalase disproportionate:

2H2O2 → 2H2O + O2

Catabolic reactions provide raw materials and energy to start up various anabolic activities (www2). According to Brooker, Widmaier, Graham and Stiling (2008), catalase is a type of enzyme found mainly in the liver cells where they break down toxic hydrogen peroxide into less reactivegaseous oxygen and water molecules which is useful to the human body. Catalysts are not used up in reactions but affect the rate of the reaction by reducing the amount of activation energy required (Brooker et al., 2008).

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Enzymes are globular proteins and have a three dimensional shape (www3). They are biological catalysts which speeds up the rate of chemical reactions without been used up (www3). Allen and Baker (1982) states that, extreme variations in the concentration of hydrogen ions and substrate concentrations could change the structure of the active site and disrupt the substrate from binding to the active site and this will prevent the formation of the enzyme substrate complex. Enzymes will be denatured, if the optimum ph and substrate concentrations at which they work best are altered and this will result in inactivity of the reaction (www3). Catalase works best at high levels of substrate concentration and ph levels, therefore the higher the concentrations of each variable, the more oxygen will be produced when molecules of hydrogen peroxide are free (Brooker et al., 2008).


*See laboratory schedule*.

The two independent variables in the investigation were ph and hydrogen peroxide. Each individual enzyme catalase has its own ph and substrate characteristics, this is as a result of the hydrogen and ionic bonds that make the unique primary structure of an enzyme.

The 5 ranges of substrate concentrations used for the experiment differed from each other in terms of concentration. The ph levels differed from each other but during the experiment, 1ml of the different levels of ph was added to 1ml of 10 % hydrogen peroxide.

The dependent variable in the catalase investigation was the volume of oxygen measured.

The controlled variable in this investigation were the temperature of the room, size and number of potato discs used for the experiment because this was the variable that made the results of the investigation valid.


Below are the results for the reaction of hydrogen peroxide in the presence of potato catalase.

Table 1: The effect of different substrate concentrations on catalase activity.

H2O2 concentration

Volume of oxygen measured (ml)


Test 1

Test 2

Test 3






















Fig 1: Attached

The optimum condition for the substrate concentration was 30 %. The line of best fit is a straight line through the origin then the reaction rate had a slight curve before the optimum substrate level was reached.

Below are the results for the reaction of ph in the presence of potato catalase.

TABLE 2: The effect of different ph levels on catalase activity in potato.


Volume of Oxygen Measured (ml)


Test 1

Test 2

Test 3


























Fig 2: See attached

The optimum ph level for the enzyme catalase was 9. The line of best fit shows that, after this point the rate of the reaction decreased.


The result of the catalase investigation proves the information retrieved from the source Brooker et al., 2008 is right. The reaction increases with increasing enzyme concentration when molecules of hydrogen peroxide are freely available until the optimum level is reached (Brooker et al., 2008). The increase in the rate of reaction is limited when molecules of the substrate are in short supply and this because there are different number of variables that aids in determining the decomposition of hydrogen peroxide in the presence of the enzyme catalase. According to www1, increase in enzyme concentration means there are more active sites for the substrate molecules to bind with and greater quantity of products can be attained. At 30%, there were many active sites but insufficient number of substrate molecules to occupy the active site. From the line of best fit shown on the graph, they might be some anomalies and this would have happened as a result of slight inaccuracies, fluctuating room temperatures which may have caused the gas to expand in the boiling tube.

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The result for ph as shown on the graph shows a clear pattern of the enzyme at its optimum point and when it gradually loosed its activity and became denatured, this supports the information that was referred to in the introduction (Allen and Baker, 1982 and www2). As the ph increased the volume of oxygen produced increased until the enzyme catalase reached its optimum at ph 9. After the optimum ph level as seen on the graph, the volume of oxygen produced gradually decreased which means there were insufficient substrate molecule to occupy the active site and the enzyme catalase lost its ability to function effectively. Denaturing of enzymes is irreversible because the bonds between the 3 dimensional shapes of the enzyme has been altered.


The investigation has shown that the activity of catalase in potatoes can be affected by changes in different ph levels and hydrogen peroxide concentrations. The reaction reached its optimum at 30% substrate concentration and ph 9 respectively. Looking at the graph of both variables, it clearly shows that further increase in the ranges used in the experiment would have resulted in decrease in the volume of oxygen gas produced and there would have been free active sites with no substrate to occupy it and this will limit the reaction and radically continue to reduce the rate of reaction.

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How does pH level and hydrogen peroxide affect catalase? ›

Changes in pH do not only affect the shape of the catalase enzyme but also change the shape or charge properties of the hydrogen peroxide substrate so that the hydrogen peroxide will not bind to the active site and thus cannot undergo catalysis.

What is the effect of pH on enzyme catalase experiment? ›

The relative reaction rate (volume of oxygen evolved during five minutes) was plotted against pH. The control showed the same enzyme activity each time the experiment was run. The relative reaction rate increased with pH - up to the optimum value (around 6.3) and then decreased at higher pH values.

What is the effect of hydrogen peroxide and catalase? ›

Catalase is a key enzyme which uses hydrogen peroxide, a nonradical ROS, as its substrate. This enzyme is responsible for neutralization through decomposition of hydrogen peroxide, thereby maintaining an optimum level of the molecule in the cell which is also essential for cellular signaling processes.

How does pH of hydrogen peroxide affect enzyme activity? ›

The enzymatic activity exhibits maximum activity at pH 7.5, assessed by the potential at which oxygen is reduced to hydrogen peroxide. At higher or lower pHs, the oxygen reduction reaction (ORR) occurs at higher overpotentials, i.e., at more negative potentials.

What effect does pH have on hydrogen peroxide? ›

The efficacy of hydrogen peroxide bleaching is directly proportional to the increase of its pH. The significant increase in bleaching outcomes occurs from pH 6.0, with maximum effectiveness achieved with pH 9.0.

Does hydrogen peroxide affect pH levels? ›

Industrial strength solutions of H2O2 (30-70%) depress the pH readings obtained when using a combination glass electrode.

Why does catalase work best at a basic pH? ›

The human catalase enzyme functions best at pH 7 because below this pH catalase enzyme loses its activity and become ineffective. It becomes denaturised and ruptures its structure. It can work from pH 7 to 11.

What is the pH of the catalase reaction? ›

The decomposition of hydrogen peroxide by catalase is regarded as involving two reactions, namely, the catalytic decomposition of hydrogen peroxide, which is a maximum at the optimum pH 6.8 to 7.0, and the "induced inactivation" of catalase by the "nascent" oxygen produced by the hydrogen peroxide and still adhering to ...

Why does pH affect enzyme activity? ›

pH affects enzyme activity because enzymes are proteins that get their molecular structure via interactions between the charges of the amino acids that form the protein chains. These interactions are in the form of a hydrogen bond which is affected by the pH level.

What is the effect of hydrogen peroxide concentration on catalase experiment? ›

WHEN catalase is added to hydrogen peroxide, there is an initial rapid evolution of oxygen which lasts for about two minutes, depending on the peroxide concentration. After this, oxygen is given off at a steady rate which slowly decreases in the course of an hour.

What is the catalase and hydrogen peroxide experiment? ›

This experiment, studies the effect of substrate concentration on the rate of reaction. Discs of porous filter paper are soaked in a solution of catalase then submerged in a beaker containing hydrogen peroxide. As the reaction proceeds, tiny bubbles of oxygen form and coalesce into larger bubbles.

What is the purpose of hydrogen peroxide in catalase test? ›

This test is used to identify organisms that produce the enzyme, catalase. This enzyme detoxifies hydrogen peroxide by breaking it down into water and oxygen gas. The bubbles resulting from production of oxygen gas clearly indicate a catalase positive result.

Does catalase work better in acid or base? ›

The catalase enzyme works best around pH 7, which is pH neutral. This indicates that it works best when there is neither excess acid nor base.

What was the purpose of hydrogen peroxide in the enzyme experiment? ›

Hydrogen peroxide decomposes slowly in light to produce oxygen and water. The enzyme catalase can speed up (catalyse) this reaction. In this practical, students investigate the presence of enzymes in liver, potato and celery by detecting the oxygen gas produced when hydrogen peroxide decomposes.

How does pH affect hydrogen bonds in enzymes? ›

At low pH (acidic conditions) [H+] are high and this may disrupt hydrogen bonds and ionic bonds. At high pH (basic conditions) [OH-] are high which can also disrupt hydrogen bonds and ionic bonds.

What pH does hydrogen peroxide work best at? ›

pH 7.5 seems to be the optimum pH for electron transfer between catalase and hydrogen peroxide.

What is the effect of hydrogen peroxide solution? ›

Hydrogen peroxide can also exert a direct cytotoxic effect via lipid peroxidation. Ingestion of hydrogen peroxide may cause irritation of the gastrointestinal tract with nausea, vomiting, haematemesis and foaming at the mouth; the foam may obstruct the respiratory tract or result in pulmonary aspiration.

What is the effect of hydrogen peroxide and what are some of its uses? ›

Hydrogen peroxide is a mild antiseptic used on the skin to prevent infection of minor cuts, scrapes, and burns. It may also be used as a mouth rinse to help remove mucus or to relieve minor mouth irritation (such as due to canker/cold sores, gingivitis).

What conditions does catalase work best in? ›

In conclusion, catalase enzymes work best at temperatures around body temperature (37.5°C), and do not work as well around temperatures 30°C or lower, or 45°C or higher. I showed that temperatures affect the reaction rate between hydrogen peroxide and catalase enzymes.

Does peroxide raise or lower pH? ›

Since hydrogen peroxide is a weak acid, diluting it will cause the pH to rise slightly.

How does pH affect all enzymes not just catalase? ›

PH not only affects the activity of the enzyme, but also affects the charge and shape of the substrate, so that the substrate cannot bind to the active site, or cannot be catalyzed to form a product. In a narrow range of pH, the structural and morphological changes of enzymes and substrates may be reversible.

What pH does catalase peak? ›

The optimum pH for human catalase is approximately 7, and has a fairly broad maximum: the rate of reaction does not change appreciably between pH 6.8 and 7.5. The pH optimum for other catalases varies between 4 and 11 depending on the species.

How does pH denature enzymes? ›

Both acidic and basic pH can cause enzymes to denature because the presence of extra H+ ions (in an acidic solution) or OH- ions (in a basic solution) can modify the chemical structure of the amino acids forming the protein, which can cause the chemical bonds holding the three-dimensional structure of the protein to ...

How does pH affect the reaction rate? ›

The rate of chemical reactions can be altered by changing pH, temperature, and/or the substrate concentration. Substrates are the compounds enzymes bond to. Optimal pH increases enzyme rate of reaction while less than optimal pH decreases it.

Does catalase have pH? ›

The opti- mum pH for catalase function is 6.8. The further the pH is from this opti- mum value, the slower the reaction rate.

How is catalase affected by temperature and pH changes? ›

As temperature increases, catalase activity also increases to a point. Once the temperature increases beyond catalase's tolerance, the heat causes the enzyme to denature, which stops activity altogether. At very acidic or basic pHs, catalase denatures.

How does pH affect enzymes structure? ›

Changing the pH will affect the charges on the amino acid molecules. Amino acids that attracted each other may no longer be. Again, the shape of the enzyme, along with its active site, will change. Extremes of pH also denature enzymes.

What happens when pH decreases? ›

Decreases in pH can in turn affect other stressors, such as by increasing free metal ions, increasing bioavailability and toxicity of toxic substances, and increasing ionic strength.

Where is catalase found? ›

Catalase (EC 1.11. 1.6) is an enzyme which is present mainly in the peroxisomes of mammalian cells.

What was the conclusion of the hydrogen peroxide experiment? ›

More concentrated hydrogen peroxide produced more oxygen bubbles and the reaction rate was faster, because it produced oxygen gas rapidly. On the other hand, more diluted hydrogen peroxide reacted slowly and the oxygen bubbles were released sporadically.

What is the purpose of using hydrogen peroxide in the catalase test quizlet? ›

What is the purpose of the catalase test? It determines the ability of some microorganisms to degrade hydrogen peroxide by producing the enzyme catalase.

How does catalase prevent hydrogen peroxide from killing the cell? ›

Catalase protects aggregated bacteria by preventing full penetration of hydrogen peroxide into the biofilm. Bacteria in biofilms are protected from killing by antimicrobial agents (1, 4, 7). One mechanism of reduced biofilm susceptibility is failure of the antimicrobial agent to penetrate the biofilm fully.

What is the hypothesis for the catalase enzyme lab? ›

Hypothesis: The enzyme catalase, under optimum salt conditions, temperature, and pH level will speed up the reaction as it denatures the hydrogen peroxide at a higher rate than normal.

What occurs when hydrogen peroxide is applied to a catalase positive cell? ›

If catalase is present, the hydrogen peroxide will be broken down into water and oxygen gas, resulting in the production of bubbles (catalase positive).

What is the hydrogen peroxide concentration for catalase test? ›

For the identification of anaerobic bacteria, a 15% H2O2 solution is necessary (1). In this context, the catalase test is used to differentiate aerotolerant strains of Clostridium, which are catalase negative, from Bacillus species, which are positive (8).

What happens if catalase doesn t break down hydrogen peroxide? ›

If hydrogen peroxide is not broken down by catalase, additional reactions convert it into compounds called reactive oxygen species that can damage DNA, proteins, and cell membranes. Mutations in the CAT gene greatly reduce the activity of catalase.

What happens when you add acid to hydrogen peroxide? ›

The hydrochloric acid catalyzes an exothermic decomposition of hydrogen peroxide into oxygen and water. The accumulation of heat and non-condensable gas increases temperature and pressure in this reaction process always lead to runaway reaction and accident owing to inadvertent mixing.

What is the disadvantage of hydrogen peroxide and catalase? ›

Disadvantages of Hydrogen Peroxide

Also, unless it is stabilised, it can react with the catalase enzyme that bacteria protect themselves with, and not be as effective in killing microorganisms.

What is the optimum temperature and pH for catalase activity and why? ›

Catalase Background Information

The optimum PH of human catalase is approximately 7 and the optimum temperature is at 37 degree. Both the PH optimum and temperature for other catalases varies depending on the species.

What is the function of peroxide and peroxide effect? ›

Peroxide effect: The change in regioselectivity of the addition of HBr to an alkene or alkyne in the presence of a peroxide. The regioselectivity for the addition reactions of other electrophiles such as HCl and H3O+ are not altered in the presence of a peroxide.

What are two important uses of hydrogen peroxide? ›

Hydrogen peroxide is used to disinfect tools, bleach hair, and to clean surfaces. It's also used in oral care and horticulture.

Does hydrogen peroxide affect enzymes? ›

However, hydrogen peroxide is able to chemically modify the peptide core of the enzymes it interacts with, and also to produce the oxidation of some cofactors and prostetic groups (e.g., the hemo group).

How does pH affect enzyme catalyst? ›

The Effect of pH on Enzymes

The rate of enzymatic reaction depends on pH of the medium. Each enzyme has an optimum pH, where the rate of enzymatic reaction is maximum. At higher or lower pH, the rate of an enzymatic reaction decreases. For most enzymes, the optimum pH lies in the range from pH 5 to pH 9.

How does low pH interfere with enzyme activity? ›

At extremely low pH values, this interference causes the protein to unfold, the shape of the active site is no longer complementary to the substrate molecule and the reaction can no longer be catalysed by the enzyme. The enzyme has been denatured.

What effect does hydrogen have on pH? ›

The overall concentration of hydrogen ions is inversely related to its pH and can be measured on the pH scale (Figure 1). Therefore, the more hydrogen ions present, the lower the pH; conversely, the fewer hydrogen ions, the higher the pH.

How does pH level affect enzyme activity? ›

Enzyme activity is at its maximum value at the optimum pH. As the pH value is increased above or decreased below the optimum pH the enzyme activity decreases.

What pH does catalase work best at? ›

pH 7.5 seems to be the optimum pH for electron transfer between catalase and hydrogen peroxide. The highest catalase activity at this pH was visibly observed by the abundant generation of oxygen at the electrode surface, which agrees with the O2 generation reaction described in Equation 4.

Why does high pH denature enzymes? ›

Both acidic and basic pH can cause enzymes to denature because the presence of extra H+ ions (in an acidic solution) or OH- ions (in a basic solution) can modify the chemical structure of the amino acids forming the protein, which can cause the chemical bonds holding the three-dimensional structure of the protein to ...

What pH is best for enzyme activity? ›

In general, an enzyme has an optimum pH. Although most enzymes remain high activity in the pH range between 6 and 8, some specific enzymes work well only in extremely acidic (i.e. pH <5.0) or alkaline (i.e. pH >9.0) conditions.

What type of reaction is catalase and hydrogen peroxide? ›

Catalase acts as the catalyzing enzyme in the decomposition of hydrogen peroxide. Nearly all living things possess catalase, including us! This enzyme, like many others, aids in the decomposition of one substance into another. Catalase decomposes, or breaks down, hydrogen peroxide into water and oxygen.

Why do enzymes work better at higher pH? ›

Each enzyme works within quite a small pH range. There is a pH at which its activity is greatest (the optimal pH). This is because changes in pH can make and break intra- and intermolecular bonds, changing the shape of the enzyme and, therefore, its effectiveness.

How does H+ affect enzyme activity? ›

Increasing the hydrogen ion concentration above pH 5.0 causes a slow increase in the rate of destruction of pepsin. 3. Decreasing the hydrogen ion concentration below pH 5.0 causes a very rapid increase in the rate of destruction of the enzyme.

What happens to catalase at low and high pH? ›

Catalase pH Levels

In humans, catalase works only between pH 7 and pH 11. If the pH level is lower than 7 or higher than 11, the enzyme becomes denaturated and loses its structure.

What pH does catalase react? ›

The decomposition of hydrogen peroxide by catalase is regarded as involving two reactions, namely, the catalytic decomposition of hydrogen peroxide, which is a maximum at the optimum pH 6.8 to 7.0, and the "induced inactivation" of catalase by the "nascent" oxygen produced by the hydrogen peroxide and still adhering to ...

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